IMMUNOHISTOCHEMICAL EVIDENCE FROM COLOCALIZATION AND DENERVATION STUDIES FOR 4 TYPES OF SUBSTANCE P-CONTAINING NERVOUS STRUCTURES IN THE RAT SUPERIOR CERVICAL-GANGLION

Four types of substance P-immunoreactive structures have been distingu ished in the rat superior cervical ganglion by double-immunofluorescen ce microscopy: (1) A major population of mainly varicose fibres enmesh ed singly-scattered neuronal perikarya, some of which contained vasoac tive intestinal polypeptide-immunoreactivity. These substance P-immuno reactive fibres did not contain colocalized calcitonin gene-related pe ptide (CGRP) and were absent after transection of the cervical sympath etic trunk. (2) A rather small substance P-immunoreactive fibre popula tion with colocalized calcitonin gene-related peptide-immunoreactivity was distributed in a patchy manner and disappeared after cutting the postganglionic branches. (3) Most of the intraganglionic small intense ly fluorescent (SIF) cell clusters were intensely substance P-immunore active. SIF cells were not visibly changed in number and fluorescence intensity by either surgical procedure. (4) Immunoreactivity was not v isible in principal ganglionic neurons of control ganglia, but occurre d in cell bodies after pre- as well as after postganglionic nerve tran section. Some of the substance P-immunolabelled perikarya in addition revealed immunostaining to antisera against the catecholamine-synthesi zin enyzme tyrosine hydroxylase or against the neuropeptides leu-enkep halin and vasoactive intestinal polypeptide, respectively. The results strongly suggest that, in addition to a substance P-containing pregan glionic input (1), and a supply by substance P-containing sensory axon collaterals (2), the superior cervical ganglion of the rat gives orig in to a paraganglionic (3) and a postganglionic (4) substance P-immuno reactive intrinsic system, the latter becoming visible only after disc onnection of the sympathetic pathway.